Cool, love the colors/pattern. It's on the inside? Did you do stick-stack, then twist the hell out of it? My wife used to do some nice looking koi pipes years ago, back when she still did glasswork (she quit during pregnancy/breastfeeding of our son, and still hasn't picked it up again). Hers were similar, but just frit on the inside, and she had a different approach to the fins. She would attach a big blob of clear, heat it, mash it with masher pliers, heat and pull into a fin shape, then fume it a bit. Worked out really well.